Years ago I had a .32 rimfire that had a bolt hole into the chamber for the bolt that held the trigger mechanism to the barrel. I put a very lightly greased cartridge in the chamber and then pushed some "plastic steel" in the hole and screwed the screw it. That eliminated the problem of the case pushing into the hole. I doubt it would work well for a high pressure round, but for a shotgun shell it ought to work well.

If I intended to use the original chamber I would do something similar Gene. A little dab of JB Weld in the hole from the chamber side and you would never know the difference. This one has a very rough bore and will be used for a glue in stub job.